Method of burning fluid fuel



Aug. 23, 1932. H. L. DOHERTY' 1,872,907

METHOD OF BURNING FLUID FUEL Original Filed Jan 22, 1925 2 Sheets-Sheet 1 H EN RY L DOHER'TT Aug. 23, 1932. H. DOHERTY METHOD OF BURNING FLUID FUEL Original Filed Jan. 22, 1925 2 Sheets-Sheet 2 N% Q m QN um www m & N U Q% 0 m mm NR .wm

HENRY L. DOHERT! @3513 h is dike 614mg m nanny L. IDOHERTY, or Ew' oRKiI. Y.,- ASASIGNOR 'ro' COMBUSTION u'rI LIT IEs con-- Patented Aug. 23, 1932 ronATIoN, or NEW 'YoRK, N. Y.,--A CORPOBAT-ION or -MAI1\T-E 'METHOD or isunume FLUID FUEL Original application filed January '22, 1925, Serial No. 3,901 Divided and this application filed -Septeii1her 12, 1929.

The present invention relates to the combustion of fluid fuels, and moreparti'cularly to an improved method of burning liquid fuel. This invention was originally described in my application Serial No. 3,907, filed Jan. 22, 1925, of which this is a division. The domestic, oil burning. systems previously developed havein general been limited to the use of a relativelyhighpriced quality of oil. Also, they often givetofian unpleasant odor. Moreover, both the gas burning systems and the oil burning systems have been relatively expensive 'to operate and complicated in construction as compared with coal burning systems. b

One object of the invention is to provide a method of burning fuel in adornestic furnace by which a relatively errpensiveand 4,, readily inflammable fuel such as gas is usedfor the normal load-heating purposes of the furnace with the supply of gas hein'g limited to a fixed amount and when more heat -is required than will he provided by the fixed amount of gas, it will be supplemented bye relatively cheap and not'ea'silyinflaminable fuel such as the cheaper grades ofoil. U

Another object of'the present invention is to provide an odorless method ofbu'rrli'ng oi-l 1 in domesticheating systems.

A further object of-the present invention to provide a method capable of satisfac torily burning heavier-, and'therefore cheaper oil, than is now commonlyus'ed' in automatic house heating systems. 1

The novel features .ot 'thle present invention are pointed out with particularity III-the pended claims.

The invention, together with further ob iects and advantages, will bestbe understood from the-following description taken infconnection with the accompanying 'drawings, in which 1 1 Fig. 1 is a View of an apparatus adapted to operate in accordance with the nieth od offihe present invention; the view beingpartly diagrammatic, parts shown'ln sect1ons,'1and parts in elevation for purposes of illustrations Fig. 2 is an elevation-on a larger scale of the gas burner and gas controlhngportion Serial No. 392,068.

ofthe apparatus illustrated in Fig. 1, parts being-shownin section; 1. .1 F ig. S'is a plan of aportion of the *gas burner illustrated in Fig. '2 a Fig. 4 is a vertical, central section of the oil drawback deviceillustratedin-Figrli Fig; 5 :isa plan ofzthezloil burner illustrated 1. 2.1 I. :2

Fig.- 6 is a section of the oil burner taken on the line 6l6 of Fig.5, looking irrt' hedirec-v tion of-thearrows. I .i [In the drawings, 10 is a'boiler, illustrated as being vone otan ordinary 11011561 heating type,'and having a furnace 12within'which- 1s a burner apparatus'll. In 'installling an apparatus such as 14 in a coal burningifurnaee in accordance with the present invention gthe ordinaryv coal T burning grates a-rerremove-d and sheet metal plate 16'is placed inrzthe lower portion of the furnace 12,:said-plate resting on the lugs l8ordinarily used to sup-.4 The sheet 16 is. centrally' port the grates. apertured to-receive the burner apparatus 1:4: which projects up into the lower tp0rt10n;.o?l

the furnace '12. Apparatus 1 4: "is mounted-at one end of a flue or air box 20 whiche'xtends into the ash p'it22 ofrth'e furnace "12 through the ordinary doorway for removingnithe ashes. m f :3:

The burner apparatus llcomprises a gas burner 26 and an oil burner 28,]ourner 26ubeing of annular or ringlike ,torm having? a centralopening throughfiwhich burner: '28 projects Gashurner 26, Figs. 2 andfil, in.- cludes a considerable number of individual burnertips .30 extending-in wring-around its upper edge and-has alsoanumher of-tips 32 adjacent the upwardly proje cting tips: 30, V I but inclined inwardly somewhat toward the center oft-he burner 26, so that fiamesdfrom attempt is made to provide means for adjust ing the apparatus to a non-luminous flame.

plate or button 38, which is made of cast iron,

or fireclay, and so positioned as to contact I with and spread oil flame issuing from the oil burner 28 and insure the thorough mingling of the oil and oil flame from burner 28 with the gas and gas flame from burner 26. The 7 upper edge of cylinder 34, moreover, 1s

notched asillustratedat 39, Fig. 1, so that flame from burners-26 and 28 may spread and issue from the cylinder 34 somewhat laterally as well as upwardly.

It is well known that notall'typ'e s of boilers areequally efficient when fired by gas..

When the amount of 'hot gases passing through the the boiler is small as compared to the size of the fines of the boiler, the efficiency often suffers unless the heating surfacesreceiveheat by radiation. The apparatus according to the present invention is radiates to a relatively large amount of heat ing surface. Burner 26'can be readily arranged to radiate to a large heating surface in-comparison to the energy of the gas being burned when the-burner is installed in an ordinary domestic type. of coal burning boil er furnace, such boilers having ordinarily a considerable percentage of their heating surface 111 position to receive radiation from a coal fire on the grate. Moreover, when the system according to the present invention is applied to a domestic type boiler, the space I designed 'to be occupied by coal and ashes is available to receive heat by radiation from burner 26. It will be clear from the drawings that the active surface of the boiler is not reduced according to the presentin'vention by refractory materialplaced against it to promote the combustion of the oil. Therefore,

when the apparatus is adjusted to give a'lu minous flame, the flame issuingfrom cylinder 34 radiates directly to all parts of the boiler surface which would receive direct heat or radiation from a coal fire. As it is good prac-,

tice to burn fuel oil with a luminous flame, no

when the oil is being burned. I

According to the present invention, moreover, the cylinder 34 has a ring of apertures 40 therein at a level slightly above the ends of the burner tips 30 whereby products of combustion may be circulated by induced draft from the furnace fireboxint'o the flame and assist in improving eflicient combustion of the oil. 7

Great difficulty has been experienced heretofore in using fuel oil for domestic boiler furnaces because the amount of oil burned iscomparatively small, the fuel often has a very high viscosity, and is quite dirty. Ac cordingly, the oil does not feed uniformly to the burnersand the" ignition is not regular nor the combustion sufficiently uniform and complete to maintain in the furnace the high temperatures necessary for proper combustion. In accordance with the present invention an ideal conditionfor burning heavy fuel oils is provided by burning gas within a refractory chamber to maintain a radiating surface which will readily ignite fuel oil.' To this end the gas is used as the normal load fuel and is burned within the cylinder 34 in amount sufficient to meet the normal heat requirements of theboiler. When the require ment of heat from the boiler increases above normal, the ,oil is introduced through the burner 28., At this time the gas is burning at its maximum amount. Therefore the oil is introduced into a heated chamber and into 7 a burning gas flame. VVhenthe combined combustion of. the oil and gas has supplied the heat requirements of the boiler'the oil will be cutoff from the burner 28 before the gas is turned down in the burner26, and" accordingly the amount of oil being burned is substantially uniform and is in sun'flcient amount to maintain an efficient and ideally burning luminous oil flame.

The means for supplying gas and air to burner 26 and for regulating a flow of the same as above described and accordingto the present invention will. nowbe described in detail: I

Pipe 42 (Fig. 1). is connected to a gas'supply which may be the ordinary city gas. Pipe 44 is taken off from pipe 42 and leads through the flue 20 to a pilot burner 46 adjacent the gas burner 26. Pipe 42 is extended within the flue 20 and connected to deliver into a chamber 48 of an air and gas proportioning and'mixing device 50 suspended within flue 20 by a bracket 52. The device 50 has a mixing chamber 54 which opens into the flue 20 by way of passage 56 and which connects with the gas chamber 48 by an aperture or passage 58. The gas flowing through aperture 58 drawsair through passage 56 and the air and gas after mixing in chamber 54 pass through the'pipe 60 within flue 20 to the gas burner 26. In order that the flame of the burner 26 may be'regulated as desired, a needle valve 62 is arranged to govern the passage 58, valve 62 being projected as a pin or like form backwards through the wall of chamber 48 opposite passage 5 8 and being slidably mounted in the wall of the chamber 48. The-outer end of the valve 62 is :fixed to a cap 64slidably mounted on pins 66 fixed inlugs 68 onthe exterior of the device 50. c The cap 64 when moved up againstthe end of the device 50 covers the air passage 56 and shuts off the flow of air to the mixing chamber 54. At the same time cap 64 carries the valve 62 into such .a position that it closes the gas aperture 58. Therefore by moving the cap 64 in one direction or the other on pins66, the flow of air and gas to the burner 26 may be regulated as desired and the cap 64 is so ar-. ranged with respect to the valve 62 and the intake end of the air passage 56 that a desired percentage mixture ofgas and air is maintained in the pipe and burner 26. The air admitted to mixing chamber .54 through passage 56 is primary air in accordance with the ordinary nomenclature of the,

art. A damper is arranged to control the admission of air into the fine 20 through )pening 71, damper 70 being operated through 7 link 72 connected to a bell lever 74 which operates the cap 64 and needle valve 62, bell lever 74 being pivoted to a bracket 76 fixed to the part 52. One end of bell lever 74 is connected to rod 78 and automatic means is provided for operating the rod 78 in accordance with the need for heat to be delivered by the system ofwhich the burner apparatus 14 is a part.

If the burner apparatus is part of a house heating system, the automatic ineans just mentioned includes a thermostat 80 placed in the room whose temperature it is desired to control. Thermostat 80 includes two fixed contacts 82 and 84, respectively. It also includes a movable contact arm 86, the position of which is controlled by the temperature of the room on account of the expansion and contraction of the curved metal portion 88. is an electric motor supplied by current through wires .92 from the power line 94. The circuit of motor90 is extendedthrough wires 96,98 and to thermostat 80, wire 96 being normally connected to fixed contact 82, wire 98 being normally connected to the arm 86 and wire 100 being normally connected to fixed contact 84. Wire 100 is also connected to an automatic thermostat or circuit closing device 102 by means of a branch 101 while wire 98 is interrupted at point 104 and connected to the arm 86 through the loop 99 running through the device 102.

The parts of the fuel and air controlling devices are illustrated in Fig. 1 in the posi tion assumed by them whenthe burner 28 is inactive. The room whose temperature is controlled by thermostat 80 will therefore be cooling off. Assuming that the temperature of the room has declined to the lower limit desired, the arm 86 of the thermostat 80 strikes the contact 82. The motor 90 is so constructed that each time its circuit is closed, it turns its driving shaft 180 degrees and then stops. The circuit of motor 90. havingbeen closed as just mentioned, the motor thereupon rotates its shaft, 180 degreesfrom no part of the present invention. The details of motor 90' are therefore neither dis-v closed nor claimed herein. i

The crank or arm 106 fixed to the shaft or motor .90 is thrown down by the movement of the motor just mentioned and the spring 108 placed in tension. Spring 108 connects the arm 106 with cord 110, cord 110 running over pulleys 112 and connecting to a cross head 114 carrying the rod 78, previously mentioned. The downward pull on the spring 108 tends to lift the cross head 114 and thereby open the gas valve 62 and passage 56 to bring up the gas flame of burner .26. YWhen, however, the temperature of the room is at the upper desired limit, arm86 of the thermostat 8.0 strikes the fixed contact .84 again closing the circuitof :motor 90 and causing said motor shaft to execute another half turn or rotary movement of 180 The arm 106 is thereby again thrown upward into thePosition illustrated in Fig. 1, the tension .of spring 108 being relaxed andthe arm78permittedto drop to close off the flow of gas to burner 26;

-However, according to the present inventionit is preferred thatthe gas flame be increased gradually and turned ofi gradually, and for this purpose .a retarding means is connecteduto the cross head 114, said retarding means comprising a rod 116 fixed .to cross head 114 and extending into the dash pot cylinder 118. Within the dash pot 118, rod 116 is connected to a weighted piston 120, (Fig. 2), the dash pot 118 being filled with light oil, preferably a mixture of kerosene and light lubricatingvoil, and the ends of the dash pot above and below the piston 120 connected by pipe 122 (Fig. 1), having a.retard-, ing valve124 therein. "When'the spring 108 has-been tensioned by the motor 90 as above described, the tension of the spring iscresisted-bythe .weight of piston 120 andthemotion of the weight of piston'12O ismoreover retarded by the oil in the dash potiso that the crosshead 114 carrying the operating rod 78 .can rise only gradually and the fuel to burner26is turnedon gradually. Similarly, when the motor 90 is turned into the position; illustrated in Fig. 1 so that the spring 108 isrelaxed, the'weighted piston gradually 94 has turne same according to the present inventionwill now be describe'd.l 1

. The'movablecross he'ad carries an .insulated contact 126.= Aco-operating contact 128 is mounted on-and' insulated from" the fixed standard 130, the latter mounted on dash pot cylinder 118. Contact 126 strikes contact 128 at. theupper limit of travel of cross-head 114 as it moves upward under the influence of spring 108 as previously described. Also, thecontacts 126 and 128 separate as soon as crosshead 11.4 starts downwardly when the tension on spring 108 has been relaxed. Contacts126 and 128are'insert'ed .in the circuit of vmotor 132, which drivesa pump 134 furnishing oil to oil burner 28. 1 The circuit of motor 132 is taken off the power line or circuit 94 through lead 136, passing. through contacts 126 and 128 to the ca'singof motor 90 andthence through lead 137 to an emergencycircuit opening device 140 and thence by lead 142 tothe casing of motor 132 itself from which it returns to the other side of power circuit 94 by lead 144. From the foregoing,it will be seen that the oil pump 134, and hence the oil burner 28, is thrown into operation only after the operat ing rod 78 has reached the upper limit of its travel and hence after the gas burner 26 is operating at maximum rate. It will be seen also that'oil pump motor 132 andpump 134 will be stopped by breaking the circuit of motor 132 at contacts 126, 128 as soon as the rod 78 controlling gas valve 62 starts down ward to shut on gas to burner 26.

The casing of oil pump 134 is supported from that of oil pump motor 132 and the shafts of the motor and pump are directly coupled in alinement. Also intermediatejoil pump 134 and motor 132 is an air pump 136 furnishing air for atomizing oil from pinupv 134 in'burner 28. The casing of air pump 136 is fixed'to the casings of motor132'and pump 134 and its shaft is inaliriement with those ofthe motor and oil pump,motor 132 and pumps 134 and 136 forming a unitary structure. 138 andis forced to -burner28 through pipe 145. Air pump 136 delivers air for atomizing the oil through pipe 24 previously mentioned,

T pipe 24 running between pump 136 and burner When pump 134 has been operating to force oil to burner28 and is then shut down by one of the automatic controls previously described, unless means were prov1ded topre- .vent it, oil would stand in the upper part of the burner 28 when not operating. As the up per part of burner 28 is surrounded by a ring of gas jets 'from burner tips 30 and 32, oilv so standing in burner 28would be carbonized Oil flows topump 134through pipe by the heat andewould' soon clog burner 28.

To prevent carbonizing of oil in burner 28,1a

draw-back device 146' is provided in pipe 145 intermediate pump 134 and burner 28. De-

vice 146, details'of which are set out below, 3 acts automatically to cut-oft pump 134 from burner 28 as soon as the'pressure of oil in pipe; 145 drops upon shutting'down of pump 134 and'device 146 then acts to suck back into its own casing some of theoil in pipe 145, so that the oil in burner 28 is drawn down below the. level at which it can be carbonized byheat-from burner 26. I

The two devices 102 and and on'the boilers, respectively, previously mentioned as forming part of the system according to the present invention operate only under abnormal conditions. Thermostat device 102 comes into operation upon the extinction of pilot 1ight'46r When the thermostat in device 102 is maintained at normal temper,- ature by the heat from pilot light 46 contactsare made to connect the two halves of 140, at the burners loop 99 so that wire 98 acts as a continuous 7 wire leading to thermostat arm 86 as previously described. When, however, device 102 cools below a certain temperature it connects wire 101.with loop 99. The action of device102 when it cools down therefore is the same as that of thermostat when the thermostat is heated up and upon the connection of wire 101 with loop 99 by device102, motor90 if notalready in thatposition turnsv arm' 106 to point upward, thereby first cutting oil the oil, it the pump is in operation and then gradually cutting off the gas.'

Device 140 controlsonly the oil-pump motor 132. lVhen the temperature or pressure with in the boiler 10 exceeds certain desired limits, device 140 disconnects wire 142 from wire 137, thereby interrupting the circuit of motor 132 and shutting down this motor and oil-pump 134. The oil to burner 28 is thereby'shut oil.

Secondary airas well as primary air for the gas flame is furnished through opening 71, as previously mentioned. However, damper 70 governing opening 71 is opened substantially fully before'the oil pump 134 is started, a, very small movement of contacts 126 and 128 one way or the other being suffi cient to start or-stop oilpump motor 132." The damper 70 is adjusted to give'the. roper supply of air for themaximum flowo gas to burner 26, while primary air for oil burner 28 is, supplied through pipe 24, so that it is clearan additional supply or airis needed to furnish secondary air to burner 14 when oil as well as gas is being burned For the purpose just mentioned there is provided a secondair inlet aperture 310m air duct 20, aperture 310. being closed by damper 312 except'when oil is being burned. Damper 312 is illustrated as hinged at 314to the outside of the top surface of-duct '20 whereby this if the damper 312 were so placed that it did" not close by its own weight some means would need to be provided to hold it normally closed.

' In order to open damper 312 when needed, a

link 316 is connected to'the unhinged end of the damper, link 316 being pivoted in turn to arm or lever 318. Lever 318 is pivoted at the end removed from link 316 to a fixed standard 320. Lever 318 lies above and is connected to a flexible operating diaphragm 322, diaphragm 322 being attached so as to close the upper end of cylinder 324 which is mounted on the duct 20. A pipe 328 connects the interior of air pipe 24 with the in-' terior of cylinder 324. beneath diaphragm 322. With this arrangement the same air pressure is maintained in the cylinder 324 as in the pipe 24. Therefore when the air pump 136 isput into operation the diaphragm 322 will be actuated to open the damper 312 to admit secondary air. f

At the instant the motor 132, pumps 134 and 136 have been shut cit by the automatic.

nated by numeral'146. The details of device 146 are illustrated in Fig. 4. Oil from pump 134 is delivered to the device 146 through a port 2? 8 in its upper portion. Port 278 leads into a valve chamber 280 in-the bottom of whi ch is a ball valve 282 carried on spindle 284 and controlling an outlet port 286. Port 286 leads into chamber 288 from which, when.

the pump 134 is delivered oil under pressure,

the oil passes to port 290 thence through pipe 145 to the oil burner. The valve 282 is held open so long as the pump is in operatiomby the pressure of oil introduced into the pressure chamber 296 in the lower part of the casing of device 146. The upper side of chamber 296 isclosed by a diaphragm 298 whose edges are clamped between-portions of the casing of device 146 as indicated'at 300. The lower side of chamber 288 is form-ed by a plate 302 fixed within device 146 by screws 304. Fixed to diaphragm 298 at one end and plate 302 at the other is a resilient plaited cylinder 306 which tends to thrust the dia-" phragm 298 downwardly; The spindle 284' of valve 282 is connected to diaphragm 298 the positionwhich they assume when the oil The means for accom phshing this result has been referred to prevl ously 1n connection with Fig. land desigpump 134 is stopped, the port 286 being closed" by the valve 282. If now the pump is started, oil pressure is transmitted: to 'the chamber 296 through pipe 292 and lifts the diaphragm 298. At first, themovement of the diaphragm 298 does not disturb the valve 282 on account of the lost motion connection between the diaphragm and the valve spindle Further upward movement of the dia- 284. phragm 298, however, brings the diaphragm into contactwith the head 308 of spindle 284 and the movement of the diaphragm thereupon lifts valve 282 and permits oil to flow through dev cc 1446 on its way to the oil burner 28. As soon as oil has filledthe chamber'288,

interior of cylinder 306.

the position of the diaphragm 298 so long as the pressure is maintained in the chamber 296,

since the area of diaphragm 298 exposed-to the oil on its under-surface is greater than that exposed to the oil within the cylinder 306, the diaphragm therefor-e continuingto hold valve 282 open. As soon as the pump is shut down, pressure is taken ofi of the underside of. diaphragm 298 and the resiliency of cylinder 306 forces the diaphragmdo'wn wardly. The first effect of the downward movement of the diaphragm298andicylinder 306 is to permit the valve 282 to. close." Afterv valve 282 has closed, diaphragm 298 may move further downwardly due .to lost motion connection between the head 308 of the valve drawn into the chamber288 from the portion.

ofpipe 145between the device 146and burner 28, thereby lowering the level of the .oil in burner 28 below the influence of the gas flame from burner 26 and preventingthe' Carbonize.

tionof oil while. standingin burner 28. i

The details of oil burner 28 are illustrated in Figs. 5 and 6. The oil or other liquidfuel entersburner28 at the bottomthrough pipe 145; and passes into'a chamber 330, the to-pof which is formed by an internal horizontal web 332. The air for burner 28 is pumped thereinto from the pump 136 through: the pipe 24, connecting with the burner through threaded offset 334 connecting with the air chamber 336 lying. within the-burner 28above the web 332. From the chamber 336the .air is conducted upwardly through a nipple 338 leading out of the chamber 336into a burner cap. 340. A pipe 342extends through the web 332 and runsfcentrally throughgchamber 336 and nipple 338. to. conduct oil to the? burner :1 it passes from chamber'288 around thevalve stem 284 at the point 310 so as to fill -the- The pressure withthe cylinder 306, however, does notafiect' cap 340. At the upper'en'd of pipe 342 is, a

nozzle 344 co-operating with the cap 340 and producing oil flame. Cap 340 has 'a central upwardly tapering opening 346 therein and ,theupper end of nozzle 344 tapers upwardly" parallel to the taper of the aperture 346 and,

projects within this aperture, but nozzle 344 is spaced from the .cap 340 so that air may pass up around the nozzlethrough the aperture 346. Nozzle 344 has a central aperture 348 leading upwardly and delivering oil within the aperture 346 so that air and oil are thoroughly commingled in passingthrough the upper portion ofap'erture 346. In order to furtheratomize the oil and thoroughly mix itwith the air, the upper end ofthe opening 348 in the ,oil nozzle 344 is enlarged and cap 340 has also a series of air jet apertures 350 arranged aroundthe central aperture 346 and so inclined as to .deliver fine ets of air under pressureto the streamiof mixed'oil and air issuing from-aperture 346. Inorder to pro moteithe ease of drilling the apertures 350 the'upper end of the cap 340 around the aperture 346 is indented or countersunkto form a depression 352. Moreover, in order to produce-a large volume of flame and also to assist in mixing the oil thoroughly. with air the apertures 350 are disposed in helically inclined relationto'the radii from the centre of cap 340so that the air jets from the apertures 350 produce a swirling action of theflame. 7

. The operation of the apparatus disclosed herein will be obvious to those skilled in the. art fromthe foregoing description. For conf venience of reference however theoperation of the apparatus according to the present" invention will be summarized asfollows: The fuel burning and combustion regulatingapparatus of the present invention is appliedspecifically to' a'domestic' heating furample, 70 F the burners will'be turned ofl and nothing butthe' pilot burner 46 will be burning. At thetime the temperature falls below 70 F. the thermostatSO will operate to close the power circuit to the motor 90 and at this time the dash-pot mechani sm11 8 will be operatedby the motor to adjust the needle valve 62 and. air'valve 64 so that the gas will be introduced intothe inix'inglpipe and flow to' the gas burner 26. The dash pot 5 mechanism is so arranged that the gas will be gara e gradually'increased until a predetermined 1 maximum orv fixed supply of gashas been reached; When the maximum has been reached electric contacts 126 and 128 mounted on the dash pot mechanism will'bemade and the air and oil pump motor 132 will'be set in operation to supply oil and air to the oil burner 28. By the time the gas supply has gradually increased to its'maximum,' the refractory. chamber surrounding the gas burner will be highly heatedand therefore when the oil is introduced into the burner28; it will be atomized into the gas flame from the burner'26 and into the heated refractory chamber 34. At the time the motor 132 is set into operation the oil will be supplied to the regulating mechanism 146 in a fixed amount, and the amount of oil flowing to the burner will be uniform as long as the oil burner con I tinues to operate. The oil is supplied to the burner 28 in a measured quantity, the measuring being accomplished by the pump 134; so

that the oil. flows through-a comparatively large pipe to a burnerhaving a comparatively large discharge orifice. When the gas is turned on by the motor 90 the air valve in the duct 20 is gradually opened as the supply 7 of gas increases. This furnishes the primary and secondary air'for the gas flame. When theoil is turned on primaryv air is introduced by the pump 1% and the secondary air is introducedinto the'duc-t 20 through the opening310 by the regulating diaphragin322' which is operatedbythe air pressure used in the 011 burner.

While the oil is burning the gas isburning at its maximum rate andthe oil burns-at a predetermined fixedrate. These two combined fuels then continue to burn until the heat supplied by the boiler is sufiicient to raise the tempera'turein the room of the house in which the thermostat is situated to normal temperatura'when the thermostat will make such an electrical contact that the motor will be operated to set the dash pot mechanism in a position for turning ofithe oil Immediately upon "the operation and gas. of the motor for turning ofl" the O1]. and gas the electrical contact for controlling the circuit of the oil and air pumpwill be broken, and the motor will stop. As soon as the oil pressure in the feed line and the air pressure in the airline have been deoreased'the suck-back'device '146 will act to draw back the oil from the burner 28 and the damper 312 will be closed. The 'gas however will not be cut off immediately, but the supply of gas M will be gradually reduced by the dash pot until it will be entirely cut off unless in the meantime the room temperature has fallen; so that the thermostat 80 will be operated to actuate the motor for again turning onthe gas. In this way the gas is used as the normal load fuel to be gradually increased andde creased as the heat demands requirel, When,

however, the temperature in the house is such as to require more heat than can be supplied by the burning of the gas alone, then the oil will be turned on to supplement the gas in supplying the heat demands. The temperature and pressure controlling device 140 is used to prevent the development of an excess temperature in a water boiler or an excess steam pressure in a steam boiler whereby the.

burning of fuel may be checked before injury occurs to the boiler. The safety device 102 which is connected with the pilot flame is arranged to operate at the time the pilot flame is extinguished in order to out off both the oil and gas to prevent them from being supplied to the furnace when the fuel is not ignited or burning.

It will be seen that the present invention provides a fluid fuel combustion method particularly adapted although not limited to household heating purposes in that it is fully automatic, but safe and rugged in operation. Moreover, the system operating according to the present invention burns fuel oil without odor and with little noise. 7

While the foregoing disclosure is specific in character the appended claims are not to be construed as limited to details of said disclosure except as to details positively included in the claims.

Having described my invention, I claim:

1. A method of burning oil comprising atomizing the oil with air in ignitable relation to a surrounding ring of gas flame.

2. In burning oil the step comprising atomizing the oil with air in ignitable relation to a surrounding ring of luminous gas flame.

3. The method of burning oil, which comprises atomizing oil with a fluid atomizing agent supplied under pressure and burning the atomized oil in ignitable relation to a gas flame and supplying air for combustion in controlled amount to produce a. luminous flame from the burning oil and gas.

4. The method of burning oil and gas which comprises atomizingoil with air and jetting the atomized oil into ignitable contact with a surrounding ring of gas flame.

5. In burning oil and gas the steps comprising atomizing oil with air, jetting the atomized oil into ignitable contact with a surrounding ring of gas flame, and introducing products of combustion into the gas and oil flames.

6. The method of burning. oil which comprises, projecting a gas flame of substantial heating capacity across the discharge orifice of an oil burner, and jetting atomized oil from said orifice through the center of said gas flame in ignitable relation therewith.

In testimony whereof I aflix my signature.

HENRY L. DOHERTY. 

